why does the tail light quit working when the turn signal stops working?

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I can't think of any reason why the tail light/brake light should be wired into the turn signal relay

And it shouldn't be.

Since you started the Sourcing Wire thread, I'm gonna go out on a limb and guess that your wiring harness is a mess...

If your TAIL LIGHT is going out when your T/S RELAY fails it must be receiving power from it - and it should not be.

The TAIL LIGHT circuit (main block terminal #58 (Black/Gray)) also powers the INSTRUMENT LIGHTS, the CLOCK and VOLTMETER lights, and the PARKING LIGHT (in the head light. Do these lights also fail when the T/S RELAY goes south?

A BLACK/GRAY wire should be connected to terminal #58 ON THE TAIL LIGHT. If it is not, what color is?

... my tail lights quit working.

You only have one tail light, right? The turn signals are not both steadily illuminated at the same time... ? Correct?

I would also be looking into why your t/s relays keep getting killed (which is different than just "dying".) Something is not right there- if i think back on it, i have had exactly ZERO t/s relays die on a m/c in the last 35+ years.

The TAIL LIGHT and BRAKE LIGHT should receive power from two separate terminals on the main contact plate inside the headlight housing. If they do not come on when the RELAY is removed it is because they are receiving power from the RELAY circuit - which is incorrect.

The TAIL LIGHT > from terminal 58 (gray/black wire; on the contact plate in the head light) which is energized by the gray wire when the ignition switch (terminal 58) is turned on.

The BRAKE LIGHT > terminal 15 (green/black wire; on the contact plate in the head light) which is energized by the GREEN wire when the ignition switch (terminal 50) is turned on. The GREEN/BLACK wire feeds the front and rear brake light switch - the wire(s) coming out of the two switches are GREEN/RED and go to the BRAKE light terminal 54 in the housing.

2. the blinker will only blink for so long, before it stops blinking for a little while. If shut off, it starts working again in 5-10 minutes.

Your RELAY is overheating and failing (again).

3. The blinker indicator will fail if left on for too long. THis too, resumes function, if left off for a while...

The INDICATOR is fed directly from the RELAY by a BLACK/WHITE wire which is connected to terminal KBL on the RELAY. If the INDICATOR LIGHT is failing it's because the RELAY is failing.

The TAIL LIGHT circuit (main block terminal #58 (Black/Gray)) also powers the INSTRUMENT LIGHTS, the CLOCK and VOLTMETER lights, and the PARKING LIGHT (in the head light).

Do these lights also fail (go out) when the T/S RELAY goes south or is disconnected?

Have you opened up the headlight housing and taken a look at the contact plate to verify correct connections per the wiring diagram?

"It is what you discover, after you know it all, that counts." _ John WoodenLew Morris
1973 R75/5 - original owner
1963 Dnepr

Since you started the Sourcing Wire thread, I'm gonna go out on a limb and guess that your wiring harness is a mess...

If your TAIL LIGHT is going out when your T/S RELAY fails it must be receiving power from it - and it should not be.

The TAIL LIGHT circuit (main block terminal #58 (Black/Gray)) also powers the INSTRUMENT LIGHTS, the CLOCK and VOLTMETER lights, and the PARKING LIGHT (in the head light. Do these lights also fail when the T/S RELAY goes south?

A BLACK/GRAY wire should be connected to terminal #58 ON THE TAIL LIGHT. If it is not, what color is?

You only have one tail light, right? The turn signals are not both steadily illuminated at the same time... ? Correct?

May I ask where these colour diagrams are from? I have the B/W ones from PowerBoxer.de linked to from Snowbums site but they are blurry and difficult to read. I am looking for schematics like these for my 1982 R100RS.

Lew refers to Stephen Bottcher's page which has quite a few diagrams. Snowbum also has some diagrams, but I don't think they're in color, at least not most. The diagram that Lew references above in his post is from a we'll maintained website that is mostly about the 1978 models, but has quite a few other interest articles and brochures. The diagram that was posted is about half way down this page: